The long term goal of this research project is to gain insight into the folding/unfolding pathways of proteins by structurally characterizing their kinetic intermediates via time-resolved infrared spectroscopy (TRIR). How proteins achieve their native, folded structures from unfolded polypeptide chains constitutes one of the foremost questions in biophysics because of its implication for rational protein design and folding-implicated disease states. The answer necessitates a structural description of the intermediates in the protein folding process on time scales ranging from nanoseconds to tens of seconds. However, current experimental observations of folding/unfolding dynamics are limited to milliseconds or longer due to the "dead time" of the stop-flow techniques used to induce protein folding/unfolding process. to circumvent this time limitation for studying the structural changes associated with protein folding, a new technique has been developed in the past two years. In brief, a fast laser pulse creates a rapid (100 ps or less) temperature jump (T-jump) of up to 30 degrees C while a second laser pulse detects and characterizes the intermediates. Since proteins can be thermally denatured by such temperature changes, it is now possible to study the dynamics of the unfolding process with a resolution seven orders of magnitude faster than previously possible. In the proposed set of experiments, ribonuclease A (RNase) will be denatured through a laser- initiated T-jump and its early unfolding events will be structurally characterized on a nanosecond to millisecond time scale.